Various environmentally-friendly vehicles including a fuel cell vehicle, an electric vehicle, a hybrid vehicle, and a plug-in hybrid vehicle are provided for improving fuel consumption under the enhanced regulations of exhaust gas.
A plug-in hybrid vehicle can charge by using common AC power, and drives in a charge depleting mode (CD mode) and a charge sustaining mode (CS mode) according to a state of charge (SOC) of a battery.
The CD mode is an electric vehicle (EV) mode of driving by using power charged in the battery. In the CD mode, the SOC of the battery is good and available power is sufficient, therefore the vehicle generally drives by using power of a motor except under special circumstances.
The CS mode is the same as the hybrid electric vehicle (HEV) mode of driving by combining power of the engine and the motor after usage of power charges in the battery. In the CS mode, since the SOC of the battery is not sufficient and usable power is relatively low, the vehicle is driven by combining power of the engine and the motor, so it is possible to improve fuel consumption and appropriately maintain the SOC of the battery.
In CS mode of the plug-in hybrid vehicle, shifting control can be performed the same as a conventional hybrid vehicle. That is, in the CS mode, the shift-speed is determined according to the engine efficiency.
However, in the CD mode, since the engine is virtually not operated and the plug-in hybrid vehicle drives by discharging the battery, it needs to minimize fuel consumption when shift-speed change is performed.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the inventive concept and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.